Piston pump for rarefying air and other gases



PISTON PUMP FOR RAREFYING AIR AND OTHER GASES Filed Jan. 17, 1925 2Sheets-Sheet 1 Dec. 14 1926. I 1,610,940

H. FRIBERG PISTON PUMP FOR RAREFYING AIR AND OTHER GASES Filed Jan. 17,1925 2' Sheets-Sheet 2 J 2 5g I? a 4? .j ygnfor" A 2 I W 1 Patented Dec.14, 1926.

UNITED STATES HJALMAR F RIBERG, F STOCKHQLM, SWEDEN.

PISTON PUMP FOR RAREFYIN G AIR AND OTHER GASES.

Application filed. January difficulties, and to produce a piston pump 1by means of which a very high vacuum may be obtained. For this purposethe inve ution consists principally in the combination of the featurethat the spring-loaded suction and pressure valves of the pump arecombined 2U with one or more actuating members-cams or the like-which isor are coupled to the pump piston, or to the driving means of saidpiston, and which member is arranged in such manner that at thebeginning of the suction stroke of the piston it causes the spring loadto act on the pressure valve and positively opens the suction valve, andat the beginning of the pressure stroke of the piston it causes thespring load to act on the suction valve, and finally vduring thepressure stroke it relieves the pressure valve from the spring pressure,and the feature that the pressure valve, is formed as a lid of the pumpcylinder which lid is arranged entirely outside the cylinder and ismovable in'a direction towards and away from the one open end of saidcylinder, while the suction valve is located in the face of the liddirected towards the pump piston.

40 By this arrangement of the positively controlled and operated valves,which will thusbe sure to open and close at the right moments, it ispossible to reduce the clearance space practically to nil, as the twofaces of the pump piston and of the lid directed towards each other maybe given suchshapes that.they=' fit tightly to each other, and nopassages are required between the cylinder and the valves. With a pistonpump of this type it is therefore possible, as practical testshavejdemonstrated, to producea very high and very nearly completevacuum, so that the pump may advantageously replace 17, 1925, Serial No.2,975, and in Sweden October 17, 1924.

the considerably more expensive and fragile mercury air pumps heretoforeused for this purpose.

In the accompanying drawings a few different embodiments of theinventionare illustrated by way of example. Fig. 1 shows in longitudinalsection a vacuum pump according to the invention with the pistonoccupying its highest position, and Fig. 2 shows the same pump with thepiston in its lowest position. Fig. 1 also shows a constructional formof the means for providing perfect tightness between the piston and thecylinder, and Fig. 2 shows another constructional form of such means.-Fig. 3 shows a piston construction with a third embodiment of the Ypacking means. Fig. 4 shows, also in lon- 7 gitudinal section, a secondembodiment of the vacuum pump, and Fig.6 shows a detail of thisembodiment. Finally, Figs. (Sand 7 show two further modified embodimentsof the pump.

In the pump illustrated in Figs. 1 and 2, 1 denotes the cylinder, and 2denotes the pump piston, which is provided in the usual manner with,elastic packing or piston rings 3 placed in circumferentiallyextendinggrooves, and is driven by a driving shaft provided with a crank, aneccentric, or the like,'not shown in the drawing. On the upper open endof the cylinder which is formed as a plane rim, a hollow cylinder lid 4is provided, which forms the pressure valve of the pump, and which forthis purpose is provided on its upper side with a cylindrical projection5 by means of which the lid is guided in a yoke 6 or the like, which isrigidly connected with the cylinder .1, or the pump frame, in suchmanner that the lid is slidable in vertical direction towards and awayfrom the cylinder 1 and may tightly close said cylinder at its upperend, see Fig. 2. In the lower face of the lid 4 directed towards thepiston 2, which face is plane, as is also. the upper face of the piston2, a suction valve 7 is provided the stem 8 of which extends through thecavity 9 in the lid and, packed in suitable manner, through theprojection 5, so that its upper end projects some distance beyond saidprojection. In the hollow projection 5 and surrounding the stem 8 thereis provided a coil spring 10 which tends to close the suction valve 7.'Finally, the

lid 4 is provided with a tubular inlet 11 intended to be put incommunication with the- ,which is not illustrated in the drawing, saidshaft extending at right angles to the stem 8 and being connected bymeans of'a suitable gearing, such as for instance gear wheels, a chainand sprocket wheels, or the like, with the driving shaft of the pump insuch mannor that it rotates with the same number of revolutions as saidlatter shaft in the direction indicated by the arrow in Fig. 1. A cam 13is secured to the shaft 12 right above the stem 8, said cam forming inthe present instance the above-mentionedactuating member whichcooperates with the suction and pressure valves. The cam 13 actua-testhe stem 8 so that the suction valve 7 is positively opened at thebeginning of the suction stroke of the piston 2, and also one arm 14 ofa two-armed fork 15 which is pivotally journalled on a knife edge 16 atthe end of an arm 17 secured to the cylinder 1, and the other arm 18 ofwhich is intended to actuate the projection 5 of the lid 4 forming thepressure valve. The arm 18 is provided with an aperture through whichthe stem 8 extends and in which it is freely movable. The fork 15 isactuated by a strong coil spring 19 which, according to the position ofthe cam 13, forces the arm 14 against the c am, or the arm 18 againstthe projection 5 and thus the lid '4 against the cylinder 1.

In the position of the various parts illustrated in Fig. lithe pumppiston 2 is supposed to have reached its highest position in which thecylinder lid 4 forming the pressure valve is raised slightly from thecylinder and rests on the piston 2 tightly bearing againstthe upperplane face of the piston. The suction valve 7 is then closed. When thepiston 2 begins its downward movement, that is to say, its suctionstroke, the shaft 12 is rotated in the direction of the arrow, when thearm 14 loses the support of the cam 13. Owing hereto the pressureexerted by the spring 19 will instead be transmitted through the arm 18to the cylinder lid 4, so that said lid will immediately move along withthe piston in the downward direction and will be forced with a certainpressure against the upper end of the cylinder 1. 'The spring load isthus brought to, bear on the pressure valve immediately at the beginningof the suction stroke of the piston, so that the pressure valve willthen immediately be securely closed. Immediately after the pressurevalve has been closed in this manner, the cam 13 begins, upon furtherrotation of the shaft 12, to actuate the stem 8 and force said steindownwards while compressing the spring 10, so that thus the suctionvalve is positively opened without the piston having In the positionofthe various parts shown in Fig. 2, the piston 2 is assumed to havereached its lowermost position, in which the cylinder lid isstilldepressed by the spring l9, and the suction valve is held open by thecam 13. When the piston 2 starts its upward movement (the pressurestroke) the shaft 12 continues its rotation in the counterclockwisedirection. The cam 13 now releases the stem 8, after which the spring 10immediately closes the suction valve 7. On the continued upward movementof the piston 2, that is, on the continued rotation of the shaft 12, thecam 13 begins again to actuate the arm 14 so that the fork 15 is turnedupwards and the arm 18 is raised from the projection 5. Owing hereto thelid 4 is relieved of the pressure from the spring 19, so that the lidmay easily be raised by the air meanwhile compressed in the cylinder,and the air may freely flow out between the lid 4 and the upper rim ofthe cylinder 1. Shortly before the piston 2 again reaches its highestposition in which it projects slightly above the upper end of thecylinder 1, Fig. 1, its plane upper face will come to bear against thelikewise plane lower face of the lid 4, owing to which all air is forcedout. The pump has thus practically no clearance space.

It-is a well-known fact that the usual elastic packing rings. 3 do notcompletely prevent air from. being drawn in between the piston and thecylinder walls, particularly when a high vacuum is about; to be reached.As even the very smallest air quantities which may in this manner passinto the suction chamber of the pump, considerably reduce the degree ofrarefactionwhich may be attained by means of the pump, means areprovided for producing perfect tightness between the pump iston and thecylinder.

In the pump 'il ustrated in Fig. 1 there is for this purpose provided inthe upper portion of the piston 2 a cavity 20 which communicates throughfine passages 21 with tho grooves in the circun'iference of the piston,in which the tightening rings 3 are placed. The cavity 20 is filled withoil. which during the operation of the pump when vacuum is produced inthe grooves, flows out into said grooves and fills the existing small.leaks. In the bottom of the cavity 20 an oil tube 22 Eli you

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is inserted, the length of said tube being so which opens when thepiston 2 and the tube 1 move downwards, and thus allows oil to flow intothe tube 22, but which closes when the tube again moves upward so thatthe oil is prevented from flowing back. The device th-us acts as an oilpum which pumps oil into the cavity 20, which is thus always filled.Such oil as will possibly flow out between the upper rim of the cylinderland the lid 4, is collected in a groove 25 extending around thecylinder, from which groove the oil may be returned through the tube 26to the receptacle 23.

In Fig. 2 a second construction of the packing means for preventing airfrom passing into the suction chamber of the cylinder 1, is shown. Anannular'receptacle 27 isprovided on the outside of the cylinder, saidreceptacle being filled with oil. The position of the receptacle on thecylinder is so chosen that the oil chamber surrounds the uppermostpacking rings 3 in the piston 2 when said piston occupies its lowermostposition. The oil space of the receptacle communicates through finepassages 28 with the interior of i the cylinder, so that also in thiscase oil will be drawn into the existing small leaks between the ringsand the cylinder walls, and a good tightness will be obtained. Such oilas will possibly flow out between the upper rim of the cylinder 1 andthe lid 4, is also in this case collected in a groove 29 from which itis returned through a tube 30 to the receptacle 27.

Finally, Fig. 3 shows a third constructional form of the packing means.The piston 2 is provided in its upper portion with a circumferentialgroove 31 of V-shaped cross section, the sides of said groove suitablyforming approximately an angle of to each other, and its bottom beingslightly rounded. A piece of tubing 32 of rubber or other elasticmaterial is placed in said groove. The other portion of the groove isfilled by two solid elastic rings 33 having approximately triangularcross section. Finally, over said rings and the tubing 32 a likewiseelastic ring 34 of rubber, leather, or the like, having atrapezium-shaped cross section is ilaced. Then the piston 2 has beeninserted in the cylinder 1, compressed air is pressed into the tubing 32through the tube 35. The tubing 32 is thus expanded and presses directlyand through the intermediary of the rings 33 which act as wedges, thering 34 against the cylinder walls, owing to which the desired perfecttightness is attained.

The constructional form of the pump illustrated in Figs. 4 and 5 differsfrom the embodiment above described and illustrated in Figs. 1 and 2principally in that the cylinder lid 4 forming the pressure valve hasits projection 5 pivotally suspended in the free end, which is formed asa ring, of the long arm 36 of a bell crank lever which is pivoted at 37to an arm 17 secured to the cylinder 1,

and the other short arm 38 of which is actuated by the spring 19'whichtends to close the pressure valve. 'Further, the cam shaft 12 which iscoupled to the driving shaft of the pump, is located further down at theside of the pump cylinder 1, and carries three camsthe middle one 39 ofwhich actuates, throughthe intermediary of a push rod 40 and a lever 41pivotally supported on the arm 36, the stem 8 of the suction valve 7while the two cams 42 which are of equal shape and secured one on eitherside of the cam 39 actuate, through the intermediary of a hollow pushrod 43 which surrounds the rod 40 and is slidable in the arm 17', theforked-shaped end of the arm 38 for relieving the cylinder lid 4 of thepressure of the spring 19. When the shaft 12' rotates in the directionof the arrow with the same speed as the driving shaft of the pump, thefunction above described is attained also in this instance, namely thatat the beginning of the suction stroke of the piston 2 the rod .43,

on the one hand, loses the support of the cams 42 owing to which thepressure of the spring 19 is caused to act, through the intermediary ofthe bell crank lever 38, 36, on the lid 4 forming the pressure valve sothat said lid is rapidly forced against the upper end of the cylinder 1,and on the other hand, the cam 39 will positively open the suction valve7 through the intermediary of the rod 40, the lever 41, and the stem 8,and that at the be ginning of the pressure stroke the rod 40 loses thesupport of the cam 39, so that the suction valve 7 is closed by thespring 10, and finally, during the pressure stroke. the cams 42 slidethe rod 43 upwards, so that the cylinder lid 4 is relieved of thepressure of the spring 19.

According to Fig. 6 the cam shaft 12 is divided into two cam shafts 12and 12 which are journalled one on either side of the pump piston 1, andboth of which are coupled to the driving shaft of the pump so that. saidshafts rotate with the same'speed as said driving shaft. The shaft 12supports the cam 39'which, as in Fig. 4, through the intermediary of thepush rod 40 and the lever 41 actuates the stem 8 of the valve 7 and theshaft 12 supports a cam 42 which through the intermediary of the pushrod 43 actuates the bell crank lever 33, 36 and thus causes the pressureof the spring 19 to act on the lid 4, or relieves said lid of thepressure of said spring. The operation of the device will thus also inthis case be the same as that above described with reference to Fig. 4.M

The embodiment illustrated in Fig. 7 cor responds substantially to thatshown in Fig. 4, but differs from the samein that in this instance theprojection 5 on the lid 4 is slidable. in a stationary yoke 6, as inFig. 1. In accordance herewith the bell crank lever 38,

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36 in Fig. 4 is replaced by a singlearmed lever 44 which is actuated bythe spring 19 anid transmits its pressure to the cylinder li Theconstructional forms above described and illustrated in the drawings areonly to be regarded as examples, and their details mayobviously befurther modified in several various ways without departing from theprinciple of the invention.

I claim:

1. In a piston pump for rarefying air and other gases the combination ofa pump cylinder, a piston in said cylinder, springloaded suction andpressure valves, said pressurevalve consisting of a lid of said cylinderlocated outside the same and movable in directions towards and away fromone open end of said cylinder, said suction valve being located in theface of said lid directed towards said piston, and an actuating membercoupled to said piston and combined with said suction and pressure.valves in such manner that at the beginning of the suction stroke ofsaid piston said member causes the spring load to act on said pressurevalve and positively opens the suction valve and at the beginning of thepressure stroke of said piston causes the spring load to act on saidsuction valve and during the pressure stroke. relieves said pressurevalve from the spring pressure.

2. In a piston pump for rarefying air and other gases the combination ofa pump cylinder, a piston in said cylinder, springloaded suction andpressure valves, said pressure valve consisting of a hollow lid of saidcylinder located outside the same and movable in directions towards andaway from one open end of said cylinder, said lid having a tubular inletintended to be put in communication with the vessel in which the gas isto be rarefied, said suction valve of the suction stroke of said pistonsaid member causes the spring load to act 011 said pressure valve andpositively opens the suction valve and at the beginning of the pressurestroke of said piston causes the spring load to act on said suctionvalve and during the pressure stroke relieves said pressure valve fromthe spring pressure.

3. In a piston pump for rarefying air and other gases the combination ofa, pump cylinder, a piston in saidcylinder, springloaded suction andpressure valves, said pressure valve consisting of a lid of saidcylinder located outside the same and movable in directions towards andaway from one open end of said cylinder, said suction valve beinglocated in the face of said lid directed towards said piston, anactuating member coupled to said piston and combined with said suctionand pressure valves in such manner that at the beginning of the suctionstroke of said piston said member causes the spring load to act on saidpressure valve and positively opens the suction valve and at thebeginning of the pressure stroke of said piston causes the spring loadto act on said suction valve and during the pressure stroke relievessaid pressure valve from the spring pressure, an arm combined with saidmovable cylinder lid, and a spring actuating said arm so as to move saidlid against the end of said cylinder, said arm being adapted to beactuated by said regu lating member in such manner as to relieve saidlid of the pressure of said spring.

HJALMAR FRIBERG.

